Telephone system



May 9, 1933.

A. KEYSER TELEPHONE SYSTEM Filed June 22, 1932 5 Sheets-Sheetv 1 May 9,1933. A. KEYSER 1,908,365

TELEPHONE SYSTEM Filed June 22, 1932 5 Sheets-Sheet 2 If-mw Hl'ff'a dKaj ser May 9, 1933- A. KEYSER 1,908,365

TELEPHONE SYSTEM Filed June 22, 1932 5 Sheets-Sheet 3 I'nusn nr HTI-Frs1:1 Kaj s er" uQmN N Q n aw u L i L 2% Qu mig* s m N @am 52k .v .im m. bIl A. KEYSER TELEPHONE SYSTEM May 9, 1933.

Filed June 22, 1932 5 Sheets-Sheet 4 A. KEYSER TELEPHONE SYSTEM May 9,1933.

Filed June 22, 1952 5 Sheets-Sheet 5 Inman :Jr

Hlr-Exi Kss? N ww mm. SS

Patented May 9, 1933 i UNrrED STATES Annrnnn Knysna, oF BERLIN-Timm.,GERMANY, AssrGNoa 'ro-SIEMENS. a innLsxn,

AKTIENGESELLSCHAFT, OF SIEMENSSTADT NEAR BERLIN, GERMANY TELEPHONESYSTEM Application filed .Tune 22, 1932, Serial No. 618,587, and inGermany Ju1y14, 1931.

The present invention relates in general to telephone systems, and moreparticularly to systems including a plurality of series-con nectedexchanges,` and has for its object to select the required exchange inthesimplest and most convenient manner by providing the exchanges withmeans for the transmission of a definite number of impulses over eitherone or the other or vboth speaking leads of the junction line, andt'oidentify the required exchange according to theinumber of` impulsestransmitted and the lead utilized' transmitted by seizing the junctionline VLA over a group selector in the individual exchanges A1-A4.

If, for example, a subscriberof the exchange A1 wishes to set up aconnection with a subscriber of the exchange A2, the junction line VL isswitched over to the group selector GVVl at contacts 13u-16u when therepeater Ucl (Fig. 2) is seized'over the access 2 of the group selectorGWl, and an impulse is transmitted over the alead which causes thejunction line VL in the repeater U62 (Fig. 3) to be switched overatcontacts 53rd-#587.41 to the connecting devices in the exchange A2.

Should a .subscriber of the exchange A1 wish to communicate with asubscriber of the exchange A3, two impulses are simultaneouslytransmitted over the a and Z) leads.v This causes a changeover (atcontacts 185103- 189u3 in Fig. 4) to the devices in exchange A3. Thesame type of changeover operation I wish-es to speak to a subscriber ofexchange A3. l

The exchange A4 is denoted by the transmission of an impulse over the blead when a subscriber of exchange Al, A2, orA3 requires a connectionwith a subscriber of ex-f change A4.

In opposite direction the following conditions are setup over thejunction line VL. For a connection between a subscriber vof the exchangeA4 and a subscriber of exchange A3, an impulse is first transmitted overthe b lead and then another impulse over the a lead. If a subscriber ofthe exchange A3 or A4 wishes a connection with a 4subscriber of exchangeA2,'two'impulses in succession are sent out over the b'lead. Shouldl asub` scriber of exchange A2, A3, or A4 wish to communicate with asubscriber Iof exchange A1, it will be necessary to transmitan impulseover the b lead for the purpose of de-k noting they exchange A1.

Fig. 2 shows the repeater Uel'of the exchange A1, Fig. 3 the repeaterU62 of exchange A2, Fig. 4 the repeater U e3 of A3, and Fig. 5 therepeater U64 of vexchange A4.

A description of the switching operationsY to be switched over from thegroup selector GWS to group selector GWl vby opening its Acontacts 13uandy 14u and'by closing 15u plied to the a lead of the junction lineover contacts 29e, 38u, 1901, and 18e.

Relay C1, energized on the seizure over* the group selector GWl, causesthe followenergized.` Relay U causes the junction line ing circuit to becompleted for relay D earth, contact 201, relay D, resistance V172,battery, earth. The short circuit for relay D over contact-s 902, 801,and 1203 is removed at contact 801. A short circuit still remains forrelay D, however, over contact 4d and resistance 'W. The resistanceratios between the resistance W and relay D', however, are so calculatedthat even when relay D is shortcircuited over contact 4d' and resistanceW, this relay operates and remains energized over contact 3d. Relay Dopens contact 6d and closes 7d, causing relay E to be energized over`earth, contact 7d, relay E, resistance 7, battery, earth. Relay E cutsoff the superimposed direct current at contact 290. The IJ lead of thejunction line VL is then switched through over contact 2201. Theapplication of superimposed direct current to the Z2 lead over contact280 is prevented by the opening 'of contact 2701.

This superimposed direct current iniiuences the identification receivingrelays X and Y provided in the individual repeaters of the exchanges A2and A3. Preceding these relays a lamp has been connected up which makesit possible to cause the relays to be influenced only by superimposeddirect current without theserelays being connected direct to thejunction line.

The switching operations brought about in the individual exchanges A2-A4by the impulse transmitted .over the a lead are described in connectionwith the repeaters U02-U04 in .the exchanges A2-A4 show in Figs. 3-5.

The setting of the connecting devices in the required exchanges iseffected by'means ofY impulse series transmitted in known manner overthe junction line with the aid of the dial switch provided at thesubscribers stations.

The 0 lead in the group selector GWl is cut ofi in known manner at theend of the conversation so that the circuit'which, after relays D and Ehave been energized, extends over the 0 wiper of the group selector GWl,access 2 to the junction line VL, relay C1, relay U, contact 5cl,resistance We', battery,

`earth, is also cut oit. Relays C1 and U,

therefore, release. Relay U causes the junction line VL to be switchedover to the group selector GWS at contacts 13u-14u while superimposeddirect current is applied tothe TZ lead over earth and contacts 2801,2701,

2602, 2503 when relay C1 releases. This superimposed direct current isapplied until relay E has restored its contacts to normal. This,however, only occurs when relay D has been short circuited' due to theclosingv of contact 801 In consequence of this short circuit, relay Dreleases with slow action, with the result that it only restores itscontacts to normal after adeinite period and short circuits relay E byopening contact 7d' and closing contact 6d. This causes relay E also torelease with slo-w action, resulting in its contacts being returned totheir original positions only aiter an extended period. The rapidenergization but slow release of relays D and E has the eii'ect that theiden tification impulses are applied a short time only, whereas theimpulse transmitted over the Z) lead at the end of the connection lastslonger. This latter impulse causes the release of the repeaters utilizedin the correspond ing. exchanges.

lf a subscriber of exchange A1 wishes to speak to a subscriber ofexchange A3, two impulses, that is to say one impulse transmitted overthe a lead andanother over the lead, are simultaneously sent out in themanner indicated in Fig. 1. The transmission of an impulse over each ofthe a and ZJ leads is eiected by the seizure oi the junction line overaccess 3 of the group selector (HV1. Relays C2 and 'U are energized whenthe junction f line is seized over access 3. Relay U, in the mannerdescribed above, switches over the junction line VL to group selectorGVl, while relay C2 applies superimposed direct current to the a leadover contacts 290, 38u, 2002, and 180,' and to the lead over contacts290, 38u, 2101, and 2302. This superimposed direct current is cut offfrom the 0; and leads when relay D is energized due to the closing ofcontact 1002, remains energized over contact 3d, and consequently bringsabout an energization of relay E over contact 7d. Relay E is maintainedenergized over contact 310 and cuts oil the superimposed direct currentby opening contact290. Contact 280 is, therefore, closed. The opening ofcontact 2602, however, prevents the current source of supply from beingconnected to the leads of the junction line.

The switching operations carried out in the individual exchanges inconsequence of these identiication impulse-s are described inconjunction with the description of the individual repeaters in theexchanges ft2-AA.

' `When, at the end of the connection between the subscriber of exchangeA1 and the subscriber at exchange A3,'the 0 lead of the group selectorGWl in exchange A1 is cut oil, relays C2 and U release. Relay Ucompletes the switching back to normal., while the impulse for therelease is transmitted over the Z) lead in the following manner:superimposed direct current is applied to the lead of the junction lineVL over contacts 280, 2701, 2602, and 2503 when relay C2 releases. RelayC2 short circuits relay D over' contacts 902, 801, and 1203. Relay Dreleases after a deiinite period, cuts ott' its locking circuit overcontact 3d, and short circuits relay E at contact 6d.- This relay alsoAreleases after a short interval, opens its locking circuit at contact-310', and, by opening Contact 280, cuts oil the superimposed directcurrent.

If a subscriber of exchange A1 wants a connection with a subscriber ofexchange A4, j the identification impulse, 1n this case a singleimpulse, is transmitted over the lead by the seizure of the junctionline VL over access 4 from the group selector GrWl. Relays C3 and U areenergized in such a ease. Relay U, as described above, causes theswitching-over while relay C3 applies superimposed direct current to theZ9 lead over contacts 290, 38u, 2101, and 3903. Relay D is energizedover contact 1103, remains energized over Contact 3d, and causes relay Eto be operated by closing contact 7d. Relay E cuts of the superimposeddirect current at contact 290.

The release impulse at the end of the connection is transmitted over theb lead by relay C3 in this case. The 0 lead of the group selector GlVlis cut off at the end of the call which causes relays C3 and U torelease. Relay U controls the switching-over, while relay C3, whenreleasing, applies the superimposed direct current to the b lead overconf tacts 280, 2701, 2602, and 2503. Relay C3 short circuits relay D atcontact 1203. Relay D releases after a delinite period and shortcircuits relay E at contacts 6d. Relay E also releases with slow actiondue to the shortcircuit, and opens contact 280 which cuts oil thesuperimposed direct current applied to the 7) lead.

Should a subscriber of exchange A2, A3, or

A4 wish to setup a connection with a sub vselector G`W8, earth. Relay Bis energized by this impulseV over the Z) lead, but this causes noswitching operations in the group selector GWS. RelayB closes contact321) which causes relay H to operate over earth, contacts 325 and 33,51,relay H, battery, earth.y Relay H closes contact 367i and thereby guardsthe junction line against seizure from the group selector (ll/V1. RelayH also closes Contact 3471 causing relay H1 to be energized over earth,contact 347i, relay H1, resistance W3, battery, earth, relay B havingreleased at the end of the received impulse. Relay H1 remains energizedover Contact 35M independent of contact 347i and takes over the guardingfor relay H at contact 37L1 since relay H has been deenergized due tothe opening of contact 33h1.

The additional impulses transmitted from the calling stationset thegroup selector GWS and the linal selector LVV'l in Fig. 1 in knownmanner. `When an impulse of longerl duration is sent out from thecalling station at the end of the call and istransmitted over the blead, relay B in the group selector GWS is energized an extended period.Relay B closes Contact 32?) which short circuits relay H1 so thatit'releases. yThe opening of con-V tact 37i1`removes the guarding of thejunction line. The release impulse transmitted over the I) lead lastsuntil relay H1 has re-` stored its contacts to normal. ARelay H isprevented from being energized over contacts 326, and 33L1 due to therelease impulse being already ended, and consequently relay B i hasopened contact 32?) before relay H, `which is energized with slowaction, actuates its contacts.A

When setting up a connectionv between a subscriber of exchange A3 or`exchange A4 with a subscriber of exchange A2, two im' pulses aretransmitted over` the leadf on the seizure ofthejunction line VLinexchange A3 or A4 (see description applicable to Figs. 4 and 5). Theseimpulses cause thev repeater U01 to guard the junction line againstseizure inexchange A1.

lVhen a connection is set up between a subscriber of exchange A4 and asubscriber of exchange A3, an impulse is sent out over the a lead aswellv as the b lead. Theimpulse transmitted over the a lead causes noswitching operations in exchange A1, but the imp pulse sent out over theb lead sets up the guarding of the junction line although it is againremoved in the manner described below (see description applicable toFig. 4) when, after the identii'ication impulse, a release impulse istransmitted over the b lead.

The switching operations brought about` in the exchange A2 by theindividual indentiication impulses will be described below. Fig. 3 showsonly the devices particularly framed-in in Fig. 1 which areprovided in jexchange A2 and which will be called the repeater U02. This repeater U02may be seized over the junction line from exchange A1 for the setting upof a connection with subscribers of exchange A2, A3, or A4. The samerepeater may also be seized by subscribers of exchange A2 from the groupselec- `tor GW2 (see Fig. 3, top right-hand corner and Vbottom center)for the setting up of a connection with subscribers of exchange A1, A3,or A4. In addition, the repeater U02 accoi-ding toFig. 3 may also beseized from exchange A3 over the junctionl line for the setting up of aconnection between subscribers of exchange A3 or A4 and subscribers ofexchange A2 orAl.

The switching operations which take place on the seizure of the repeaterU02 over the junction line VL from exchange A1 will rst be explained.This seizure occurs when a subscriber of exchange Alwishes to set up ayA1, the group selector GVV1 in exchange A1 must be set t0 a definiteaccess which causes an impulse tobe transmitted over the a lead. 'Ihemanner in which this transmission takes place has already beendescribed. rIhe impulse (superimposed direct current) transmitted overthe a lead actuates relay X in exchange A2 over the a lead, contact39u1, signal lamp L, relay X, earth. The signal lamp L preceding theidentification impulse i vreceiving relays X and Y in Figs. 3 and 4 isof such atype that only superimposed direct current can influence relaysX and Y over it. Relay X is energized and throws over its Contact 4200,which causes winding I ofrelay T1 to be short circuited so that thejunction line AVL cannot be seized from the groupselector GVV2 over theaccesses 01 and 02'. Relay C8 then operates and maintains the circuitextending over earth, contacts 42m,

" 5701, 154s, winding II of relay T1, 0 wiper of the preselector VVVG,relay C8, Key SpT, contact 14301, resistance 71, battery, earth,independent of key SpT and contact 14301 due tothe closing of contact14208,. Theopening of contact 158:0 prevents the junction line VLfrombeing seized over the access 0.of the group selector GW2. Relay C8 takesover this guarding at contact 9008 at the end of the impulse and afterrelay X has released.

Relay X causes relay C4 to be energized over earth, Contact 40m, relayC4, battery, earth. Relay C4 actuates its contact 4104 with the resultthat relay C5 operates over earth, Contact 4104, winding I of relay C6,battery, earth.` Relay C0 sets up its own locking circuit over contact4706 which then extends over earth, contact 4706, winding II of relayC6, contact 4805, resistance WV, battery, earth. Due to the fact thatthe impulse vover the a lead of the ljunction line is of very shortduration, relay X consequently remains energized a short period only.Relay C6, however, operates before relay X releases and maintains theguarding Contact 5206. RelayCSA closes its contact 4600 which in turnVcauses relay C7 to be energized over earth, contact 4003, relay C7,battery, earth. Relay C7 then takes over the guarding at contact 5107.Ily means of'relay C7 a circuit for relays U1 and S is closed asfollows: earth, contacts 4907 and 5005, winding I of relay U1, winding Iof relay S, battery` earth. Contact 153s short circuits relay T overearth, windings I and I1 of relay T, 0 wiper of the preselector VINI),relay C12, contact 153s, earth. Relay T, therefore, releases and batteryis applied to the rotary magnet DM over earth, battery, rotary magnetDM, contact 447?, winding II of relay S1, earth. The above-mentioned.circuit for the rotary magnet DM is cut off at contact 44t when relay Tis operated over its winding III by the closing of contact 145dm. Therelease of magnet DM causesthe preselector VVV to be advanced one step.A circuit for the rotary magnet DM can only. be completed if relay T isshort circuited due to the succeed-V ing line being busy, as otherwiserelay T re-V mains energized and prevents a circuit for the rotarymagnet from being completed by retaining contact 4425 open. Relay U1, byopening contacts 53a1 and 54101 and closing contacts 55u1 and 56H1,causes the secondary lineswitch MVl to be seized which gives an accessto the group selector GVV (see Fig. 1). Theopening of contact 57u1 andclosing 58141 switchesthrough the 0 lead to the secondary lineswitchMlVl to which a second winding of relay U1 is connnected and whichmaintains relay U1 energized. Relay C8 releases due to the changeover ofthe 0 lead and causes relay C13 to operate over earth, contacts 138101,139s, g wiper of the preselector VWS, relay G13, resistance W, battery,earth. Relay C13 applies superimposed direct current to the lead overcontacts 12101, 13209, 123013 until relay C8 is energized over earth,contact 144013, relay C8, key SpT, contact 14301, resistance WL battery,earth. Relay C8 short circuits relay C13 by actuating its Contact 14008,thus causing said relay to release after a certain period andconsequently restore its contacts to normal. rIhe opening` of contact123013 then cuts off the superimposed direct currcnt. This long impulsetransmittedl over the lead, the duration of whichY is determined by theslow action of relay G8, causes the release of the devices in the otherexchanges A3 and A4 reached over the junction line VL and actuated bythe identificationy impulse transmitted over the a lead.

Relay Sis the last to be energized during the release, aswill bedescribed hereinafter, and disconnects the junction line VL from thepreselect'or VVG by opening contacts 1528 and 68S, and at the same timeremoves the guarding potential by opening contact 1548, with the resultthat the junction line between exchanges A2 and A3 is released. Afurther connectionmay, therefore, be set up in both directions betweenexchanges A2 and A3 over'the unction line VL, and, due to thepreselector VW5 having been set to an idle line leading to exchange A1,a connection to this exchange also may be completed. Relay Y1 serves asan identifying receiving devicel for connections from the exchange A3completed over the junction line VL, and is now connected to the b leadover contact 94106. Relay U6 is energized over earth, contact 105u1, Zwiper of the switch VlV, relay U0, battery, earth.

The setting of the group selector GV5' and the final selector LW2 inexchange A2 (see Fig. 1) is effected in any known manner of no interestin the present case. i

At the end of the conversation a long impulse is transmitted from theconnecting devices in exchange A1 over th-e Z) lead of the junction lineVL and this impulse actuates relay Y, which causes winding Il: of relayC6 to be short circuited at contact 591g, so that said relay C6releases. The release of relay C6 cuts off the circuit for relay C7 atcontact 4606. Relay C7 also restores and at Contact 4907 breaks thecircuit for relays U1 and S. Relay S, being a slow-acting relay, is thelast to remain energized, and,.by opening its contact 153s, removes theguarding of the junction line VL from exchange A1, and at thesame timeconnects the junction line from exchange A1 to the preselector VW6 byclosing its contacts 152s, 68s, and 154s, with the result that aconnection may be set up over this device also.

If a subscriber of exchange A1 wantsa subscriber of exchange A3, animpulse is transmitted simultaneously over the a and b leads due to theseizure of the ljunction line VL over a definite access from the groupselector GWl in the manner described above (see description for Figs. 1and 2). This impulse causes relays X and Y, connected to the junctionline VLover the neon lamps L, to be energized. Relays X and Y, byclosing contacts 42x or 64g, guard the junction line to exchange A3against seizure by the group selector GW2, and at the same time energizerelay C8, while the junction line to exchange A1 is guarded againstseizure by the group selector GW2, due to the opening of contact 158m or1041/. Relay C8 takes over the guarding at contact 9008. Relay Xenergizes relay C4 over contact 40:0, causing relay C6 to respond overwinding I and contact 4104. A locking circuit for relay C6 extends overearth, contact 4706, winding II of relay C6, resistancel/V, battery,earth, due to relay C5 being energized over earth, contact 60g,

winding I of relay G5, contact 6107, battery,

and earth by the closing of contact g vof -relay Y. Thus the lockingcircuit for relay C6 is prevented from being completed over contact 4305and resistance W. Relay C5 re- 'mains energized over earth, Contact6205,

winding II of relay C5, battery, earth. Relay C7 is energized overearth, Contact 6905, relay C7, battery, earth. `Relays C5 and Y closetheir ,contacts 7005 and 7 111/. A circuit for relay Z is now completedover earth, contacts 7005, 71g, f wiper of the preselector Vlll, contact1513/2, relay Z, battery, earth.

VBefore relay Z actuates its contacts,the cir- `cuit over the b lead iscut oil and relay Y openscontact 711/. This again cutsoii the circuitfor relay Z. The junction line to exchange A3 is guarded against furtherseizures over the accesses 01 and 02 of the group 5 selector GW2 vbyrelays C5, C6, and C7 {contacts 6305, 5206, and 5107 `after the-,releaseof relays X and `Y according to the sequence. The junction line toexchange A1, after relays X and Y have released and consequentlycontacts 15800 and 104g/,have been closed, is, there- L fore, guarded bymeans of contact 9008. No

further operations take place in the present case on the seizure of therepeater` U02 in exchange A2. i The op-erations caused in the otherexchanges due to the two`imp'ulses simultaneously transmitted over the aand?) leads will be explained .in the descriptionv of the repeatersprovidedy in the-individualexchanges. i

`The switching means lofthe YrepeaterdU02 in Fig. 3 are. restored tonormal at .th-e end of the conversation by' means Vof a long yimpulsetransmitted Vover the b lead. Thislong impulse causes'relay Y to beenergized, which,

at contact 593/, shortcircuits bothrelays C5 which, in the mannerdescribed above, is car# ried into effect by acorresponding seizure or"the junction line VL by means of the group selector G`W1 in exchange A1.This impulse over the ZJ lead energizes relay Y. HRelayfY, as mentionedabove, guardsthe unction line ati contacts 643/ and 104g/ and alsoenergizes relay C8, which, by means of contact 9008, takes over theguardingvfor contact 104g. A circuit for relay C5V is completed overcontact 60g. Relay C5 remains energized after the release of relayYvover earth, contact 6205, winding II of relay C5, resistance W,battery, earth. Relay C5 energizes relay C7 over contact 6905. Aftertherelease of relay Y, the junction lineto exchanges A3 and A1 is furtherguarded over contacts 6305 and 51.07 by relays Cand C7. 7 i vTheswitching operations caused in the individual exchanges by this impulseover the 5 lead are mentioned in the description of the individualrepeaters in the exchanges.

The release of the switching device aftera call also effected by meansofa long impulse transmittedover the@ lead which causes relay Y to -beenergized an'extended period, and the short-circuit relay C5 at contact59g, causing it to release. Relay C5, by meansof Contact 6905, opensthecircuit for relay C7, which, in the capacity of the switching meanslastactuated, removesthe guarding of the. junction line `against beingseized by a subscriberof exchangeA2.

Vhen, for example,fa subscriber of exchange A3 or A4 wishes to setup a'connecf tion with a subscriber of exchange A2, he'has .ico

i over winding III of relay T1.

to transmit two successive impulses over the b .lead corresponding totheseizure of the repeater inexchange A3 or A4. The manner in vwhichthis is carried into effect in the individual .repeatersin exchange A3or A4 will be explained in the description of the repeaters U03 and U04(Figs. 4 and 5) in the exchanges A3 and A4.

The first impulse over the b lead, accord ing to Fig. 3, energizes relayY over the lead of the junction line VL, contacts 124013, 6509, 66010,V67 01, 0 wiper of the preseleetor VIVG, contacts G88, 53u1, lamp L,relay Y, earth. Relay Y, in the manner already described, guards theline and Yover contact g energizes relay G5, which, by closing contact6205 after the release of relay AYcloses its own locking circuit overearth, contact 6205, winding II of relay C5, resistance W, battery,earth. Relay Cenergizes relay C7 over earth, contact 6905, relayv C7,battery, earth. An energization of relay Z is prevented by the firstimpulses over the lead. Relays C5, C7, and C8 talle over the guarding atcontacts 5107, 6305, and 9008 in the manner described above. Relay C5prepares a circuit for relay Z at contact 7 005. The second impulseyover the b lead reenergizes relay Y, causing a circuit for relay Z tobe closed over earth, contacts 7005, 7111/, wiper fof preselector VWG,contact 1513/2, relay Z, battery, earth. Relay Z closes contact 7 2e,with the result that relay CI-I is energized in parallel with relay Z.`Relay CH remains energized over earth, contact 730k, winding II ofrelay CH, resistance W, battery, earth, after the end of the secondimpulse and after relay 'Z has released. Relay CI-I closes contact 740kso that the junction line to exchanges A3 and A1 cannot be seized due tothe short circuit of Winding I of relay T and windings I and II of relayT1. Relay T1 of the lpreselector VWG, which is short circuitcd, nowreleases. This applies battery tothe Lrot-ary magnet DMl of thepreselector VWG over earth, winding II of relay S, contact 74t1, rotarymagnet DMl, battery, earth. The rotary magnet DMl, when energized,actuates contact 750Zm1, thereby completing a circuit DRelay T1 opensthe circuit for the rotary magnet'DM1 so `that it releases, which causesthe switch wiper of the preselector VWG to advance one step. If thesucceeding line, to which the preselector VWGis set, is idle, relay T1of -the preselector VWG is permanently energized and vprevents therotary magnet DM1 from operating by opening contact 7 4t1. Relay CS alsois short ci'rcuited by means of contact 740k, and consequently releases.

Before the preselector VWG is advanced,

relay CH completes a circuit for relay G ex-l .tending over earth,contacts 7 6?/2, 77 07a, 7 8g, winding I ofrela-y Gr, 0 wiper of thepreselect-or VW, resistance W, battery, earth.

Relay C5 is short circuited due to this circuit. It, therefore, releasesand opens the circuit for relay C7, with the result that t-hepreselector VWG may be seized from the exchange A1 over the junctionline.

Relay G sets up a locking circuit for itselic extending over earth,Contact g, winding II of relay G, contact 7 90h, battery, earth.

Relay Y2 responds over earth, contact 88071., winding I of relay Y2,resistance V, battery earth, and remains energized over contact 973/2.This relay maintains the circuit for relays U2 and S1 independent ofcontact 81g by means of its contact 1033/2. Relay Y2 takes over theguarding at contact 89y2 in a manner similar to that of contact 7 40h.By means of contact 870k, relay GH connects up relay Y1 to the b lead,and this `relayY1, in a connection set up from exchange A1 to A2,receives the impulses over the b lead for the identiiication of theexchanges, and also re.- ceives the release impulse over the b leadafter a connection from either exchange A3 or A4 to exchange A2 has beenset up.

Relay C11 is energized over earth, contacts 147g, 14681, relay C11,contact 104g, key SpT, Contact 4302, battery, earth, before relay S1 isenergized, and applies superimposed direct current over contacts 109011,11002, to the b lead of the line leading to exchange A1 for` the purposeof releasing the devices inthe exchange A1 which have been set inoperation by the identification impulse. ,Relay D3 is connected tobattery over earth,contact 106011, relay D3, resistance W,battery,`earth. This relay remains energized over contact 115053 andenergizes relay E2 over earth, contact 112053, relay E2,jresistance W,battery, earth. Relay E2 cuts off the release current over the'b lead atcontact11002. This release current now flows over contacts 116011,11702, due to the fact that relay S1 in the meantime has opened thecircuit for relayC11 at contact 14681. Relay C11 releases and shortcircuits relay D3 at contacts 107011 and 118011. Relay D3 releases andshort circuits relay E2 at Contact 111033. This cuts 0E the releaseimpulse over the Z) lead at contact 1170.2. Relays Sl and U areenergized over earth, contact-s 31g, S20/t, winding I of relay S1, windning I of relay U2, battery, earth. Relay U2 opens Contact 83102 and 84u2and closes 85142 and 36a2. This switches the junction line from exchangeA3 to exchange A2 over to a line leading to a secondary lineswitch NVEand over this to a group selector GVV (see F ig. 1) This switching-'overoperation cuts oil the 0 lead to the preselector VVV, so that winding Iof relay T is no longer short circuited and the junction line toexchange A1 may be seized over the group selector -GVVQ (access 0). Alocking winding II kfor relay U2 is also connected up due to theswitching over of the 0 lead. Relay S1, in

the circuit for relay U2, disconnects the j unci tion Aline fromthepreselector V W5` at contacts 15581, 15681, and 15781 since relay Sl isthe last relay to be restored to normal, as will be described inconnection With the release operation. i

The setting of the secondary lineswitch and group selector GN inexchange A2 (see Fig. 1) is carried intoV eli'ect in a manner of nointeres t in the present case.

At the end of the conversation, a long impulse which energizes relay Y1an extended period of time is again transmitted over the lead. Relay Y1short circuits relay Y2 at contact 913,/1, causing relay Y2 to release.Relay Y1 also short circuits winding II of relay GH at contact 92?/1,with the result that relay CH is also deenergized. Relay CH opens thecircuit for relay Gas well as relay U2 and relay S1 at contacts 7 90hand 820k. The guarding of the line leading to exchange A3 is onlyremoved when relay CH, which is slow to release, has restored itscontacts to normal and discontinued the guarding by opening contact7407i.Y

Should a subscriber of exchange A3 or A4 require a connection with a,subscriber of exchange A1, relay Y in the repeater of exchange A2 (seeFig. will `be energized by the one impulse over the o lead which de#notes exchange A1, and, by closing contact 64?/ f causing relay CS to beenergized) and opening contact 1043/, guards the junction line.immediately upon the seizure. By closing contact (503/, it causes relaysC5 and C7`to be energized in the manner described above. Relay C8 alsoenergizes over contact 641/ and the'line is further guarded at contacts6305, 5107, and 9008 after the identification impulse has ended.` Theswitching operations occurring` in vexchange A1 on the transmissionof animpulse over the lead have already been described.l The connectionbetween 'the subscriber of exchange A3 or A4, therefore,` extendsaccording to Fig. 3, over the preselector VWG to the repeater U61 inexchangev `A1 shown in F ig'. 2. v

The switching means in Fig. 3 are restored to normal by the operation ofrelay Y responsive to a long impulse over the b lead in the mannerdescribed above.:

The impulse receiving relays X and Y also are influenced during aconnection between a subscriber of exchange A4 and a. subscriber ofexchange A3. As mentioned in the description of Fig. 1, when such aconnection is set up an impulse is first transmitted. over the f7) leadand then another impulse over thev a lead, according to the seizure ofthe junction line in exchange A4. The impulsetransmittcd over the leadenergizes relay Y, which momentarily guards the unctionl line and causesrelays C5, C?, and C8 to operate sothat they talre over the guarding ofthe line; The impulse transmitted overV the a lead cnergizesrelay X,which in turn causes relays C4 and C6 to respond. None of thel de:-viccs in exchange A2 are switched over. If the junction line, however,is switched over to the devices in exchange A3 (see Fig. 4) in anoperation to be described at a later stage, a long release impulse istransmitted over the 7) lead of the junction line tol exchange A2, andthis impulse restores vthe relays in F ig; 3 to normal in the mannerdescribed above.v

Vihen the repeater in Fig. 5V is seized from exchange A3 or A4 whileaconnectionexists over the junction line from exchange A1 to exchange A2,the junction line from exchange A1 is switched` over to the secondarylineswitch hill/J1 over which the group sel lector VGVW). is accessible(Fig. 1), said switchingbver operation being carried out over contacts55m, euhfand 58ML In such a case, the impulse receiving relaysXand Ycannot be actuated by any impulses. An auxiliary impulse receivingdevice, however,

4is connected to the b lead `over contact 94u6 it was performed by meansof contact74c7z.

Relay Y2 is energized' over earth, lcontact ?/1, winding H ofrelayJY2'-, contact 963/2, battery, earth. Relay Y2brealrs theenergizing circuit atcontact 061/2', but still remains energized overearth, contact 973/2, winding I of relay Y2, resistance l/V,'battery,`earth. By closing its contact987/2, it prepares circuit forrelay CH, due to 'fact that the lirst impulse is ended .after contact982/2 has been closed so'that a circuit for relay CH cannot be completedby the actuation or' contact 99?/1.. If thesecond impulse `energizesrelay Y1, the circuit for relay Cl'lis completed over earth, contact98?/2, winding I of relay CH, contacts 10081, 99?/1, battery.V earth.When its short circuit is removed atfcontact 9212/1, at the Y end of thesecond impulse, relay CH closes a locking circuit fer its winding Ilover earth, contact 78071., winding Il of relay GH, resistance lV,battery, earth. Relay CH causes the same switching operations lto beperformed as those described in relation to a connection being sot up,from a subscriber ot' exchange A8 or A4 to a,-subscriber ofexchange A2when the junction line from exchange A1 to A2 is idle and relayVYfoperated as an impulse receiving relay.

he release at the end of the conversation is also in this case caused by`a long impulse L. ab

transmitted over the b lead. The release impulse actuates relay Y1,which, in the manner described above, restores the switching means yofthe repeater U02 to normal.

When a subscriber Vof exchange A3 or A4 wishes to set up a connectionwith a subscriber of exchange A1 while the junction line from exchangeVA1 to exchange A2 is busy, the impulse transmitted over the b lead,which at the same time denotes the exchange A1, causes relay Y1 tooperate. Relay Y1 guards the junction line and energizes relay Y2 overearth, contact 953/1, winding II of relay Y2, Contact 96?/2, battery,earth. Relay Y2 remains energized over earth, contact 97/,1/2, winding lot relay Y2, resistance W, battery, earth. The energizing circuit forrelay Y2 is cut oil at Contact 962/2. This relay Y2 operates its contact893/2 and thus takes over the guarding of the junction line fromexchange A2 to exchange A3 as well as to exchangeAl. The circuitextending over earth, windings I and II of relay T', 0 wiper of thepreselector VVV, relay C12, contact 149012, resistance YV, battery,earth, is, therefore, shorted. Relay T consequently releases, and, inthe manner previously de'- scribed, advances the preselector Vl/V to thesucceeding idle line. Relay C12, therefore, releases yand opens contact149012. The circuit for relay G11, however, is still maintained over thekey SpT and Contact 4302.

vIn the case of a subscriber of exchange A2 wanting a subscriber ofexchange A1, it is necessary that the subscriber of exchange A2 set thegroup selector GVV2 to the access 0 (Fig. 3, lower central portion ofdrawings). This definite seizure energizes relay C11 over the 0 wiper ofthe group selector GV2 in the following circuit: earth applied to thegroup I selector Gll72, 0 lead, contact 158m, relay C11,

contact 1043/, key SWT, contact 4302, battery, earth. Relay C11 isoperated and applies superimposed direct current to the lead overcontacts 109011 and 11002. Relay X and the other impulse receivingrelays located in the other exchanges and connected to the lead cannotbe energized due to the opening of contact 108011. Relay D3 is connectedto battery over earth, contact 106011, relay D3, resistance W, battery,earth. Relay D3 opens contact 1110Z3 and closes contact 1120Z3, thuscausing relay E2 to operate over earth, contact 1120Z3, relay E2,riesistanc'e W, battery, earth. Relay E2 closes its contact 11302 and ismaintained energized independent of contact 1120Z3. It also cuts off thesuperimposed direct current at contact 11002, and switches through thelead from the group selector GVV2 at contact 14502.

The impulse transmitted ov-er the b lead energizes, in the mannerdescribed, the relay B in the group selector GW8 in exchange A1, andthereby sets up the guarding of the junction line against furtherseizures over the group selector GWl vvin exchange A1.

rThe release of the connecting devices, more particularly thetransmission of a long release impulse over the 7) lead, is effected inthe following manner: when the subscriber of exchange A2 replaces hisreceiver, the group selector- GW2 isrestored tonormal 1n the usual way.The circuit extending over the 0 lead is cut oit, resulting in therelease l of' relay C11. This relay closes its contact 116011 'andthereby causes superimposed diother subscriber of exchange A3 has to setthe group selector GW2 to the access over which relay C9 is energizedover the` 0 lead, that is to say, the group selector must be set `to theaccess 01. The circuit for relay C9 extends over earth applied to thegroup selector GV2', 01 lead, relay C9, key SpT, contact 143.01,resistance W1, battery, earth. The circuit extending over earth,resistance W, windings I and II of relay T1, 0 wiper of the preselectorVWG, relay C8, key S/QT, contact 7 14301, resistance W1, battery, earth.The circuit extending over earth, resistance W, windings I and II ofrelay T1, 0 wiper ot the preselector VVV6, relay C8, key SpT, contact14301, resistance W1, battery, earth, is consequently short circuited.Relay T1 releases, and, in the manner previously indicated, advances thepreselector VW6 to an idle junction line leading to exchange A3. RelayC9 applies superimposed direct current to the a lead over contacts 12101and 12209, and to the lead over contacts 12101, 12209, and 12509. Theopening of contacts 13609 and 6509 prevents the backward directedimpulse receiving relays connected to the and leads from beinginfluenced by the superimposed direct current. A circuit for relay D2 iscompleted over earth, contact 18809, relay D2, resistance W', battery,earth. Relay D2 opens its contact 126d2 and closes 1270Z2, which causesit to remain energized independent of contact 11809. It also closescontact 1196Z2, which energizes relay E1 over earth, contact 119cl2,relay E1, resistance WV, battery, earth. Re

lay E1 remains energized over contact 12801 l independent of contact1190Z2. This relay cuts oli'the superimposed direct current by openingcontact 12101. The opening of contact 14301 does not cause relay C9 torelease due to a locking circuit having been estab- Relay E2 o lishedover contact 141'cZ2. VContact-12061 is now closed, but the currentsource of supply mentioned is not connected up to the b lead due to theopening of contacts 67 61 and 6509. The b lead from the group selectorGW2 is now switched through over contacts 13761, 12509, and 124013. Y

The switching operations in the repeater U03, according to Fig. 4,`caused by the impulses transinitted simultaneously over the a andleads, will be described in a later paragraph.

The group selector GVV2 is released in known manner and the circuit'overthe 01 lead cut oil, so that relay C9 releases when the connection withthe subscriber of exchange A3 is ended and the subscriber of exchange A2replaces his receiver. Relay C9 now applies superimposed direct currentto the b lead of the junction line leading to exchange A3 over contacts12061, 06010, 6509, 124013, and this superimposed current is applieduntil relay D2 is short circuited by the opening of contact 11809 andclosing of 12909, sliort-circuiting relay E1 by opening contact 1190Z2and closing contact 1300Z2 and allowing the latter relay to release.ingreleasing, relay E1 cuts oil' the current from the junction line atcontact 12061. This impulse causes the release of devices shown in Fig.4 in the. manner indicated in this ligure and explained in connectiontherewith.

If a subscriber of exchange A2 wishes to speak to another subscriber ofexchange A4,

' he sets the group selector G`W2 to the access over which relay C10 isenergized over the 02 lead. The prese-lector VWG is set to an idlejunction line leading to exchange A3 by means of the circuit completedover the 02 lead, relay C10, key SpT, contact 14361, resistance W1,battery, earth. This setting operation is carried out in exactly thesame manner as that occurring when access 01 is seized.

Relay C10 applies superimposed direct current to the 7i lead overcontacts 12161, 13209, 133010, and 124013. This superimposed directcurrent is prevented from being applied backwards due to the opening ofcontacts 135010 and 66010. Relay C10 closes a circuit for relay D2 overearth, contact 131010, relay D2, resistance W, battery, earth, removesthe short circuit for relay D2 at contact 134010, and consequentlycauses relay D2 to be energized. Relay D2 remains enrelay C10 istransmitted over the b lead of the junction line leading to exchange A3.The opening' of contact 14361 doesnot release relay ()10 due to alocking circuit having been completed for this relay over contact 141d2.

The switching operations caused in the repeaters U03 4) and U64 (Fig. 5)by the impulse transmitted over the Z) lead will'V be described later.

The circuit over the 02 lead is cut off at the end of the connection.Relay G10 releases and, with the object of restoring the switching meansin the repeaters U63 and` U64 to normal, applies superimposed directcurrent to the Z2 lead onverxcontacts 12061, 00010, 0509, and 124013.The release current over the lead is only cut off at Contact 12001 afterrelay D2 has been short-circuited contacts 12909 and 134010, and hasinturn sli'ort-cii'cuited relay E1 over contact 130072. A long impulseconsequently is transmitted over the Zi lead for the purpose ofv causingthe release. It should be noted that the junction line to exchange A3 isguarded n Y for the duration of the call over access 01 or 02 as long asrelays C9 and 'C10 remain line in exchange A1 or exchange A2 in the .12

This causes relays X1 f manner described. j and V3 to be energized forthe duration of the impulse over the 0 and b leads. These relays closecontacts 132001 and 1833/3, causing winding I of relay T2 to `beshort-cir- `cuited and relay C21 to operate, which prevents the seizureof the junction line VL from exchange A3 to A4. Relays X1 and Y3 alsocause relay C14 to be energized over earth, contacts 160001 and 105.1/3,winding I of relay C14, resistance W, battery, earth. Relay C14 locks upover its contact 170014. Relay C10, however, cannot be operated due vtothe fact that the identiiication impulse over the junction line is endedand relay X1 has caused contact 190001 to be opened before theslow-acting relay C16 responds. Relays X1 and Y3 alsok open contact161001, 162001,

100g/3, and 1673/3, so that the junctionline v from the group selectorGW3 in exchange A3 and leading to exchange A2 cannot be seized. Thisguarding is taken over by relay C21 (Contact 224021). At the end of theimpulse over the a and leads and' after the release of relays X1 and Y3,relay C14 short circuits winding Ilot relay T2 over contacts 157 014,103003, and 10982, and thus prevents the junction line VL to exchange A4trombcing seized: The opening of contact 171014 removes one shortcircuit trom Winding I of relay CI-I1 at contact 164015, thus causingrelay @H1 to respond over earth, Winding I of relay (l-I1, contact 178014, resistance W, battery, earth. Relay CI-Il ren mains energized overearth, contact 1790L1,

' Winding II of relay CHI, resistance -W,'bat

tery, earth, at the end of the impulse over the bv lead and after relayY3 has removed the short circuit for relay GHI at contact 180g/3. RelayC20 is energized over earth, contacts Y 269071127082# Wipe? Of thepreselecter VWS,

relay C20, key SpT', contact 26204, resistance W, battery, earth, andbrings about the release of the switching means in exchange A4, Whichwere operated by the identification impulse transmitted over the lead,by sending out a release impulse over the Z lead. Relay C20 tor thispurpose applies superimposed direct current to the b lead over contacts251020, 25204. Relay C20 also energizes relay D5 over earth, contact253020, relay D5, resistance, battery, earth. Relay D5 energizes relayE4 at contact 2566Z5. Relay E4 cuts off the release current at contact25204. Due to the fact that relay C20 in the meantime has beendeenergized by the opening of contact 27082 (relay S2 is energized bymeans of relay CI-Il at contact 187 chl), superimposed direct current isapplied to the b lead over contacts 258020 and 25704 until relay D5releases due to a short circuit over contacts 259020 and 260020,shortcircuiting relay E at contact 261055. Relay E releases after adelinite period and cuts od the release current by opening its contact257 04. Relay @H1 closes contact 187 chl and thereby energizes relays U3and S2 over earth, Contact 1840711, rWinding I of relay U3, Winding I ofrelay S2, battery, earth. Due to the opening of contacts 168u3, 185103,and 186%3 and the closing of 187%3, 188103, and 189u3, the junction linefrom exchange A2 is switched over to the secondary lineswitch MW 3 overwhich the group selector GVG is accessible. Relay U3 removes the shortcircuit for Winding I of relay T2 at contact 168153, Which removes theguarding of the junction line against further seizures over access 0 otthe group selec tor GW3, and also opens contact 19003 Which disconnectsthe receiving device X1 from the a lead of the junction line. yRelay U3at the same time closes contact 27703, which .energizes relay U7 andcauses relays X2 and Y4 to be connected to the a and Z) leads of thejunction line over contacts 19003 and 191u7. Relays X2 and Y4 serve asreceiving devices tion line from exchange A4 is seized.

The closing of contact 19482 short circuitsV WindingsII and I of relayT3, causing relay T3 to release and apply current to the rotary magnetDM3 of the preselector 1.71477 over earth, Winding I of relay S3,contact 17 6753, rotary magnet DM3, battery, earth. The rotary magnetDM3 closes contact 177 dm3 and sets up a circuit for relay T3 overWinding III as follows: earth, contact 17 70h23, Winding III of relayT3, battery, earth. Relay T3 opens Contact 176253 kvvhich breaks thecircuit for the rotary magnet DM3 and causes the Wipers of thepreselector VVV? to be setto the succeeding idle junction line leadingto eXchange'A2. Contact 1776Zm3 is now reopened and the circuit overWinding III ot relay T3 is cut oil. A fresh circuit for Windings I andII of relay T3 can be completed over the succeeding idle junction line,with the result that the rotary magnet DM3 can no longer be actuatedover contact 176153.

Relay S2'in the circuit for relay U3 disconnects the junctionV line fromexchange A2 from preselector VVV8 at contacts 19282,

'19382, and 16052, and removes the guarding of said junction line atcontact 16382 so that the incoming line may be seized.

vThe setting or" the connectingv devices in exchange A3 is effected in amanner of no interest inthe present case.

At the end of the conversation, and Awhen calling subscriber cuts ofithe connection, a long impulse is transmitted over the 5 lead inexchangeAl or exchange A2. This impulse retains relay Y3 ig. 4)energized an extended period of time, and this relay short circuitsWinding II of relay @H1 and Winding II of relay C14 over contact 180373.vRelays CE1 and C14 release andrestore their contacts to normal. RelayCI-Il opens the circuit for relays U3 and S2 at contact ien/17u. lay S2remains energized a short perioe longer, due to its slow action, and atcontacts 169s2and 19482 prevents the seizure or the junction line fromexchange A2 or the group lselector GII/'2 in exchange A3 until all ofthe switching means have been restoredrto normal. f

It the subscriber of exchange A1 or A2 'requires a connection with asubscriber of e5;- change A4, relay Y3 is energized by the identilieation impulse for exchange A4 (an impulse over the b lead). RelayY3 closes its contact 1833/3, whereupon relay C21A isenergized and thejunctionr line is guarded against seizures from the group selector G1473for connections tor exchange A4. Relay Y3, by opening contacts 166.?/3and 1673/3, guards the line to exchange A2 from the` group selector GVV3over the accesses 01 and 02. Relay C21 (by means of contact 224021)takes -over the guarding of the junction line after Relay U3 releasesfirst, Whereas re- Y the release of relay Y3. This relay Y3 alsooperates its contact 165y3 and thus energizes relay C14, which, byclosing contact 170014, completes a locking circuit for itself overearth, Contact 170014, winding II of relay C14, resistance W, battery,earth, as soon as relay Y3 releases at the end of the impulse over the blead and opens contact 1303/3, so that the short circuit for winding IIot' relay C14 is removed. Relay C14 guards the junction line betweenexchanges A3 and A4 against seizure from the group selector GVV3 overthe 0 lead by closing its contact 167014, whereupon relay C21 remainsenergized and the junctionline from exchange A3 to exchange A0 isguarded against further seizures over access 01 or access 02 by theclosing of contact 224021. The switching operations brought about inexchange A4 by the impulse over the b lead are enumerated in theAdescription relating to Fig. 5. At the end of the conversation between asubscriber of ex'- change A1 or A2 and a subscriber of exchange A4, along release impulse is again transmitted over the Z) lead whichmaintains relay YY3 energized an extended period of time. Relay Y3, byclosing its contact 180g/3, causes winding II of relay C14 to be shortcircuited. Relay C14 releases after .a definite interval and, byrestoring its contacts to normal, removes the guarding of the line.

Should a subscriber of exchange A4 wish to set up a connection with asubscriber of exchange A3, an impulse is firstV transmitted over the blead and then another impulse over the 0 lead as indicated in Fig. 1.The impulse transmitted over the b lead actuates relay Y3 and causes thesame switching operations to be carried out as were described in thecase of a connection between a subscriber of exchange A1 or exchange A2and a subscriber of exchange A4. The impulse also causes the guarding ofthe junction line to be set up in the same manner. Due to the fact thata circuit is prepared for relay C16 by the closing of contact 195014,the succeeding impulse over the a lead closes a circuit for relay C16 bythe closing of contact 196ml as follows: earth, contacts 195014 and196001, f wiper of the switch VWS, winding I of relay C16, resistance W,battery, earth. Relay C16 remains energized over winding II in thefollowing circuit: earth, contact 197016, winding II of relay C16,resistance 7, battery, earth. By closing contact 198016, it shortcircuits relay T2 so that the preselector VWS is set to the succeedingidle junction line in the manner described above. Relay C14 is shortcircuited over earth, contacts 209016, 210,01, and 211z2, winding I ofrelay G, wiper 0 of the switch VWS, resistance IV, earth. It, therefore,releases and removes the guarding of the junction line at contact167014. Relay G1 is energized in the above-described circuit and causesrelay C22 direct current to the b lead for the purpose i of releasingthe preceding switching means which were operated by the identificationimpulse. R-elay C19 is operated over earth, contact 274022-, relay C19,key Spt, contact 17303, resistance W, battery, earth, and takes over theconnecting up of the release current over contacts 22703 and 226019.Relay D4 responds over contact 235019, remains energized over contact229cl4, and operates relay E3 over contact 230cl4. Relay E3 ismaintained energized over Contact 23103 and breaks the release currentat contact 22703. Due to the release of relay C22 by the opening ofcontact 27 2u4, and the releaseof relay C19 by the opening of contact274022, the release current is applied over contacts 24003,

247013, and 249019, until relay D4 is shortc ircuited over contacts228019 and 238018, and in `turn short-circuits relay E3 at contact2760Z4. Relay E3 releases and cuts off Vthe release current by openingits contact 24003.

Relay G16 also completes a circuit for relays U4 and S3, whichextends'over earth, contact 199016, winding I of relay S3, winding I ofrelay U4, battery, earth. Relay U4 opens contacts 200u4, 201104, and202164, and closes contacts 20304, 204u4, and 20504. This switches overthe junction line from exchange A4 to the devices in exchange A3, thatis to say, over the secondary'lineswitch MW4 to the group selector GW6#Relay C16 connects relay Y4 to the Z) lead of the junction line overContact 206016. Relay X2 cannot be connected up due to the opening ofcontact 207016.

The setting of the switchesin exchange A3 has no bearing on the presentinvention, and, consequently, will not be described.

At the end of the conversation, the repeater shown in Fig. 5 appliessuperimposed direct current for an extended period of time to the blead, with the result that relay Y4 is energized. This relay shortcircuits relay C16 ov-er contact 2037/4, so that the latter relayreleases. Relay (116, when releasing, cuts off the circuit for relays U4and S3 at Contact 199016, and these relays consequently release andrestore their contacts to normal.

It a subscriber of exchange A4 wishes to communicate with a subscriberot exchange ico and b leads over contacts 190167 and 19h67, so that theidentification impulse may influence these devices.

When a subscriber of exchange A4 in such a case desires a connectionwitha subscriber of exchange A3, the identification impulses (oneimpulse transmittedv over the leadand then another impulse over the alea-d) influence relays Y4 and X2. The irst impulse over the 7o leadenergizes relay Y4`, which guards thejunction line by means of contact220y4 and over contact 2143/4 completes a circuit "for relay H2 asfollows: earth, contact 2143/4, winding I of relay H2, resistance W,battery, earth. Contact 2203/4 short-circuits f relay T2, and, inconsequence thereof, causes `the circuit for relays U4 and S3.

ate.

the preselcctor VV'? to seize an idle line. Relay H2 short circuits itswinding I at contact 21B/t2, but still remains energized overearth,-contact -216L2, winding II, resistance W, battery, earth, andprepares a circuit for relay C16 at contact 217L2. The succeedingimpulse, transmitted over the a lead at the end ofthe lirst one whichpassed over the l;

lead, causes relay X2 to operate and complete Y the circuit for relayC16 by closing its contact 218002so that relay C16 is energized overearth, contact 217/52, contact218ar2, winding Iresistance W, battery,earth. Relay H2 takes over the guardingof the junction line at Contact219]@2, and thus prevents the seizure of the junction line over thegroup selector GVEB. Relay C16, by means of relay S3 (contacts 22183 to22383), disconnects the junction line `from the preselector VW7 andswitches it over by means of relay U4 (at contacts 200154 to 205u4).Relay C16 takes over the guardingv of the` junction line at contact198016. Also in this case the Vrelease at the ond of the conversation isbrought about byY a long impulse transmitted over the Z) lead, so thatrelay Y4, by closing its contact 208jz/4, short-circuits winding II ofrelay C16 and causes it to release. Relayl C16 then opens Relay S3 inturn cuts off the circuit for relay G1, and all the switching means arethus restored to normal. Y

Responsive to the seizure of the junction line in exchange A4, when .asubscriber of .xchange A4 wishes to set up a connection with asubscriber of exchange A2, two impulses are transmitted overthe b lead.lf, therefore, the ljunction line between exchanges A@ and A3 is busyand has been switched over (by relay U3) to the connecting devices inexchange A3, `the auxiliary impulse receiving devces relays X2 and Y4are connected to the a and Z2 leads. The irst impulse over the 'b leadcauses relay Y4 to oper- Relay Y4 energizes relay H2 over contact2143/4, which, by means of Contact 219712, takes over the guarding ofthe junction line at the end of the first impulse.

The succeeding impulse over the b lead reenergizes relay Y4. Theimpulse, however, is of short duration so that, due to the closingofcontact 2033/4, a release of relay C16 or relay H2, owing to the shortcircuit ofwinding II oi" these relays, does not occur.

rihe switching operations caused in the exchange A2 by the two impulsesover the Z lead have already been described. The release also in thisAcase is brought about by a long impulse transmitted over they Z) lead,which energizes relay Y4 for an extended period of time. Relay yY4short-circuits windings II of relays C10 and H2 at contact 208y4,

with the result that all the switching means are restored to normal inthe manner indicated above.

a subscriber of exchange A4 desires a connection to a subscriber ofexchange A1, the identification impulse (an impulse over the Z) lead)opera tes relay Y4 in'exchange A3 which guards the line and sets thepreselector VVV'? to an idle line in the manner described above. Theswitching operations taking place in exchange A1 or exchange A2 inconsequence of the impulse over the b lead have previously beendescribed.

The release also in this case is brought about by means of a longimpulse over the Z) lead.

Outgoing connections from exchange A3 are to be described below.

vWhen a subscriber of exchange A3 wants aA connection with exchange A1,the group selector (irl/V3 in exchange A3 (see Fig. 1) must be setto theaccess Vv02 (Fig. 4). This energizes'relay G19 over the 02 lead,contacts'166-t/3 and 161ml, relay C19, key SpT, contact 17363,resistance W, battery, earth. The circuit for relay C19 short circuitsrelay T3 and the preselector VV? is set to an idle line in the mannerdescribed above. Relay C19 closescontact 226019,and thereby appliessuperimposed direct current to the lead over contacts 22!- 63 and226019. 1t also energizes relay D4 over earth, Contact 235019, relay D4,resistance W, battery, earth, the short circuit for relay D4 having beenremoved atcontact 228019. Relay D4-remains cnergizedover contact'229cl4independent of relay C19 and energizes relay E3 over earth, contact230a74, relay E3, resistance lV, battery, earth. Relay E3 is maintainedenergized over contact 23103 and completes a circuit tor relay F overcontact 23263 as follows: earth, contact 11# 23263, relay F, battery,earth. Relay E3, by opening its Contact 227 63, cuts oill thesuperimposed direct current. Relays C19 and E3 disconnect the a and Y)leads from the preselector VW 8 at contact 233019 and contact 234019 or23563, whereas, due to the closing of contact 23663, the b lead from thegroup selector GW3 is connected to the junction line. The switchingoperations brought about in exchanges A2 and A1 bytheimpulse Ilthejunction line between exchanges A2 and VA3 should be busy wheny overthe b lead Vhave previously been described.

Should a subscriber of exchange A3 Want a subscriber of exchange A2, thegroup selector Gl/V3 in exchange A3 is set to the access 61, over whichrelay C18 is then energized. The circuit for relay C18 extends over the61 lead from the group selector GW3, contacts 1673/3 and 162661, relayC18, key SpT, contact 17363, resistance VJ, battery, earth. Thissliort-circuits relay T3 and sets the preselector VVV7 to an idle line.Relay C18 applies superimposed direct current to the lead over contacts22763 and 237618. In addition, relay D4 is energized over earth, contact238618, relay D4, resistance W, battery, earth, Vand maintains thecircuit for relay C18 over contact 2396Z4 independent of the key SpT andcontact 17363. Relay D4 itself remains enen gized over contact 2296Z4.This latter relay also closes contact 2306Z4, thus causing relay E3 tooperate over earth, contact 2306Z4, re-

lay E3, resistance W, battery, earth. Relay E3 remains energized overcontact 23163, and sets up a circuit for relay F over contact 23263.Relay E3 cuts oi'l the superimposed -direct current to the Z) lead atcontact 22763.

Prior to relay F being energized due to its slow action, however, thesuperimposed direct current is re-applied to the b lead over contacts24063, 241618, 2427, and 243-622, and is cut off as soon as relay Foperates over contact 23263 and opens its contact 242/. Two impulses iiisuccession, therefore, are in this case transmitted over the 5 lead independ# ence of the seizure over the 61 access. The opening ot' contacts244618, 245618, and

23563 causes the junction line to be discon-V nected from thepreselector VWS before an impulse is transmitted over the Z) lead. Theswitching operations of the devices in exchanges A1 and A2 caused by thetwo successive impulses havebeen described above.

Vhen the calling subscriber of exchange A3 replaces ,his receiver, the61 lead of the.

group selector (iT/V3 is cut oitl in known manner and the circuit forrelay C18 is opened. Relay C18 releases so that the superimposed directcurrent is applied to the b lead over contacts 24063, 247618, 249619,and 243622, until relay D4 is short circuited by the closing of contact238618 and, by closing its contact 276cl4, short circuits relay E3. Thisrelay opens the circuit for relay F at contact 23263 mains energizedover earth, contact 254d5, relay D5, resistance W, battery, earth, and

also energizes relay E4 over earth, contact 3566Z5, relay E4, resistanceW, battery, earth. Relay E4 is maintained energized over contact 25564independent of contact256d5 vand cuts ofie the superimposed directcurrent at contact 25264. This sourceot supply will not be re-appliedover contact 25764 due to relay C20 having opened contact 258620. Thepreselector VWS is advanced in consequence of the seizure over relayC20and the junction line is guarded. The switching operations brought aboutin exchange A4 by the impulse transmitted over the Z) lead will beexplained in connection with the description of the arrangement shown inFig. 5. `At the end of the conversation between the subscriber ofexchange A3 and the subscriber of exchange A4, the circuit for relay C20is cut oit, causing the superimposed direct current to be applied to theb lead `over contacts 258620 and 257 64. This current is applied untilrelay D5 is short circuited by the opening of contact 253620 and theclosing of contacts 259620 and 260620. Relay D5 then closes its contact2616Z5 and causes relay E4 to restore its contacts to normal, ywith theresult that the superimposeddirect current is cut ofi at contact 25764.This long impulse over the 5 lead `causes the release of the repeaterU64according to Fig. 5 'as will bedescribed in conjunction with thearrangement shown in Fig. 5. Y .i

When a subscriber of exchange A1 wishes to speak to a subscriber ofexchange A2, only one impulse is sent over the a lead. Thisimpulsecauses relay X1 in exchange A3 Vto be energized, which relay in turnenergizes'relay C14 over contact 160ml. Relay C14, after completing theguarding of the junctionl line,

remains energized over earth, contact 1 7 0614,

winding Il, resistance W,'until short-circuited by contact 1803/3 whenrelay Y3 opera-tes j responsive to a long impulse over the Z) lead.

Relay C14 consequently releases. TheA release impulse in this case,however, is transmitted immediately after `the. switching over to theconnecting devices inexchange A2f(see description applicable to Fig.

An impulse is transmitted over'the blead in accordance with the seizurein the .indi-i vidual exchanges A1`A3when a subscriber of exchange vA1,A2, or A3 wishes toset up a connection with a subscribe-r of exchangeA4. The manner infwhich this is carried Y out hasbeen described indetail in` the description of the arrangement shown in Figs. 2, 3,. and4. InFig. 5, the4 identification impulse overV the Z9 lead causesrel'ayB in they group selector GVW? to be operated over the lead, contacts294145 and 29105, relay B, earth. Relay B vis energized and closes itscontact 2955. No further switching operations are brought about in thegroup selector in consequence of the energization of relay B. Due to theclosing ot contact 2955,

relay H3 is connected to battery over earth, contacts 2952), 296h4,relay H3, resistance lV, battery, earth.' Relay H3 is` energized and byclosing contact 297z3 guards the junction line against seizure from thegroup selector G5574. Relay H3 energizes relay H4 over contact 293/L3,which then remains energized over contact 29954 and, at Contact 296L4,opens the circuit for relay H3.` Relay ll4tales over the guarding of thejunction line at contact 300L4. rlhe impulse transmitted over the b leadends, and relay B releases, before the circuit for relay H4 has beencompleted.

The setting of the group selector @W7 in exchange A4 is effected inknown manner.

' At the end 0I" the connection a long release impulse is againtransmitted over the 5 lead. It causes vrelay B in the group selectorGW? to remain energized for an extended period ot time, contact 2950being closed in the meantime so that relay H4 is short circuited andreleases after a time, thus restoring its contacts to normal so that.the guarding of the junction line is removed. Relay B, however, remainsenergized only until relay H4 has restored its contacts to normal, andcontact 2955, after the circuit for relay H3 has been set up overvearth, contacts 2950,

296761, relayH3, resistance YV, battery, earth,

does not remain closed due to the release impulse over the'b lead forsuch a long period that the slow-acting relay H3 is caused to function.

l/Vhen a subscriber of exchange A4 wants a connection with a subscriberoit exchange A1, an impulse has to be sent over the 0 lead f* in themanner shown in Fig. 1. This is et battery, earth. Relay D6 remainsenergized over'contact 307cl6 and, in addition, sets up a circuit forrelay E5 over earth, Contact 3080Z6, relay E5, resistance l/V, battery,earth. Relay E5 remains energized rer Contact 30965 independent ofcontact 3036076 and, by opening contact 30365, cuts off the superimposeddirect current :from the ZJ lead. It also switches through said b, leadat contact A31065. .The

opening of contact 30165 cuts ofi the abovementioned circuit tor relayC25, but the latter relay remains energized over contact 327rl6. rlheswitching operations brought about in the individual exchanges due tothe impulse over the lead have already been described. TWhen theconversation between the subscriber et' exchange A4 and the subscriberof Xchange fit1 is ended, the 03 lead 'from the group selector G`W4 iscut olif and relays C25 and U5 consequently release.l Relay U5 bringsabout the switching over ot the junction line to the group selectorGli/V7 at contacts 290u5 and 29105, while superimposed direct current isapplied to the 5 lead over the contacts 31165, 312023, 313024, and314025 due to the release of relay C25. rlhe release of relay C25 alsocauses relay D6 to be short circuited over contacts 315025, 316023, and317 024, with the result that relay D6 releases after a deiinite period,its release being re tarded by the short circuit. Relay D6 shortcircuits relay E5 at contact 3180Z6,1so that relay E5 also releasesafter an extended period of time and restores its contacts to normal.The superimposed direct current applied to the Z) lead is cut oil by theopening of contact 31165, and the release impulse over the Z) lead isthus ended.

Should a subscriber of exchange A4 re- Y quire a connection with asubscriber et exchange A2, he sets the group selector @V174 to access02. rlhis causes relay C24 to be energized in series with relay U5.Relay U5 brings about the switching over ot the junction line from thegroup selector' (ll/V7 to the group selector @rl/V4 at contacts292%5-29305, while relay C24 applies superimposed direct current to theZ) lead over contacts 30365,

30405, 30565, and 319024. Relay C24 enern gizes relay D6 over earth,contact 320024, relay D6, resistance lll, battery, earth. Re lay D6remains energized over contact 307636, and energizes relay E5 overcontact 3036Z6. Relay E5, by opening contact 30365, cuts oit thesuperimposed direct current. lt contact 31105 is now closed,superimposed direct current will be re-applied to the lead over contacts31165, 321/?2, 322624,. 319624 until, by.

means of relay E5, the relay F 2 is energized over earth and contact32365 and cuts off the superimposed direct current by opening itsrcontact 321f2. In this case, therefore, two impulses in succession aretransmitted overr the 0 lead on the seizure of the unction line overaccess 02 by the group selector GVV4. rlhe 02 lead is cut oli' at theend oi the call and relays C24 and U5, therefore, release. Relay U5brings about the switching over of the junction line to thegroupselector (ll/V7, whereas relay `C24 applies the superimposed directcurrent to the 5 lead over contacts 31165, 312023, 313024, and 314025.This superimposed direct current is intended to bring about the releaseand is applied until relay D6 restores, after being short-circ`uited bythe opening of Contact 320624 and closing of contact 317024. Relay D6,by closing its contact 318d6, short circuits relay E5 which restores itscontacts to normal after a Y definite period, and thus cuts off thesuperimposed direct current applied to the 5 lead by opening its contact31165.

When a subscriber of exchange A4 wants a connection with a subscriber ofexchange A3, he sets the group selector GVV4 in exchange vA4 to access61, which causes relay C23 to be energizedA in 'series with relay U5.Relay U5, in the manner described above, brings about the switching overof the junction line to the group selector GVV4. Relay C23 appliessuperimposed direct current to the b lead over contacts 30365, 304105,30565, and 324623. By closing its contact 325623 it energizes relay D6,which remains energized over contact 307d6 and energizes relay E5 byclosing contact 308CZ6. Relay E5 cuts off the superimposed directcurrent applied to the leadby actuatingcontact 30365. The closing ofContact 31165 causes superimposed direct current to be applied to the alead over contacts 31165, 321f2, and 326623 which, however, is cut oilwhen relay'E energizes relay F2 over contact 32365 and breaks theconnection at Contact 321 f2. In this case, therefore, an impulse is rsttransmitted over the b lead and then one over the ct lead.V

When thev connection between the subscribers of exchanges A4 and 'A3 isended, the access'of the group selector GV4 is cut 0H". Relays C23 andU5 are deenergized so that relay U5, in the manner described above,switches over the junction line to the group selector GVV?, and relayC23 applies superimposed direct Current to the b lead over contacts31165, 312623, 313624, and 314625 for the purpose of releasing therepeater U63 in exchange A3. Relay D6 releases and at contact 318cl6short circuits relay E5. Relay E5 releases after a definite period and,by opening its Contact 31165, cuts oil" the superimposed direct currentapplied to the l) lead.

It will be mentioned in this connection that when a. subscriber ofexchange A1 sets up a connection with a subscriber of exchange Aa, theidentification impulse transmitted over the a lead causes no switchingoperations to be carried out inthe repeater U64 shown in Fig. 5. Inaconnection extending from exchange A2 to exchange A3, however, animpulse is transmitted over the 5 lead as Well as-over the a lead. Theimpulse transmitted over the b lead brings about exactly the sameswitching operations (guarding by' means of relays H3 and H4) as thosebrought about in a connection Aextending from exchanges A1-A3 toexchange A4. After the repeater U63 has been switched over to theconnecting devices in exchange a3, however,

a release impulse is transmitted over the lead as previously described,and this impulse causes the switching means in the repeater U64 (Fio'.5) to be restored to normal.

As Wi l be seen from F ig. 1 and also further described in conjunctionwith Figs. 2-5,

the identilication impulses are transmitted independence upon theseizureoi the junction line VL, which interconnects all the ex-VAchanges, over a group selector of the individual exchanges A1-A4.

Fig. 6 shows a theoretical embodiment according to which the firstimpulse seizes the junction line VL, but the-impulses are trans-1numitted by means ot a special device actuated by a second impulse series.

In Fig. 6 the calling subscriber has access over a call finder AS to achange-over switch UW inV exchange A1, over which the group selector GWis accessible. When the group' selector GW is setto a definite contactrow, for example O, the switch UW is switchedover in known manner to ajunction line VL which interconnects all the exchanges A1-A4. Thejunction line is then guarded against seizure from any other station andfrom transmission of the identiiication impulse of exchange A4 (animpulse over the 5 lead). For the purpose of selecting the requiredexchange A2 or ,Y A3 between exchanges A1 and A4, the stepping switch MLis now set to a deiinite contact (3 or 4) over which an identifyingrelay C1 or C2 is energized, being simultaneously switched over atcontact u. The identifying relays @-02 correspond, for example, torelays Cl, C2, and C3 shown in Fig. 2. It an esl roo

identifying relay is not energized over the i,

stepping switch ML by the second impulse,` the group selector G1572 isset by this impulse series to a contact row over which the groupselectorV G1171 or another Vgroup of exchanges may be reached in themanner indicated in Fig. 6. w K

Connections from exchange A2 or A3 are set up in the same manner as thatdescribed in the case of a connection from exchange A1.

When a connection from exchange A4 `is set up, the rst identificationdigit causes the group selector GW in exchange A4 to beset over switchesAS and UV. In the case of a connection to another exchange, for exampleA2, the group selector GW3 is seized by the The arrangement shown inFigJG is use( when a plurality of groups of exchanges A1- A4 areconcerned and individual exchanges, for example exchanges A2`and A3,operateas subexchanges and others, for example A4 asl

